Corrosion preventive composition



United States Patent 3,294,694 CORRGSION PREVENTIVE COMPOSITIQN Andrew S. Wood and David E. Gensheimer, Paducah, Ky assignors to General Aniline & Film Corporation, NWY0i'k, N.Y., a corporation of Delaware No Drawing. Filed Mar. 10, 1965, Ser. No. 438,764 1 6 Claims. (Cl. 252-146) The invention relates to an improved corrosion preventive composition for use in non-oxidizing acid solutions to decrease the corrosion of metal in contact with said solutions.

Itis known. that propargyl alcohol is an excelent corrosion inhibitor for acid solutions. It is also known that a synergistic corrosion inhibitor can be obtained by employing as the inhibitor a mixture of propargyl alcohol and an amine such as pyridine, tributylamine, etc. The activity of the amineand propargyl alcohol is effectively synergized when the amine is employed in amounts of from 10% to 90% by volume of the inhibitor composition.

It is the principal object of the present invention to provide a corrosion preventive composition which inhibits the corrosion of various metals in contact with corrosive acids.

A further object is to provide a process for inhibiting the corrosion of various metals, such as iron, steel, nickel and ferrous alloys when in contact with corrosive acids.

.Other objects and advantages will become manifest from the following description.

We have found that a synergistic corrosion inhibiting composition is obtained by employing as the inhibitor a mixture of 95% by volume of propargy-l alcohol and 5% by volume of dipropaugyl formal. The inhibitor mixture is used at a level ranging from 0.00 l1.% by volume based on the volume of the aqueous acid solution in which the acid concentration ranges from 1 to by weight.

Various acids, especially the mineral acids, are effectively inhibited against metal corrosion by employing the inhibitor mixture. The acids include acetic, hydrochloric, phosphoric, sulfuric, and other non-oxidizing acids.

The dipropargyl formal in the inhibitor mixture has the following formula:

H O( OCHZCECH 2 and is prepared by the following procedure:

P-ropargyl alcohol (450 grams, 8 moles), s-trioxymethylene (90 grams, 1 mole), benzene (150 grams) and Dowex 50 (H form) are refluxed in a 1-liter flask equipped with a Barrett water trap. When the ternary azeotrope breaks, the lower layer containing propargyl alcohol and water is removed and the water content measured periodically. After the theoretical amount of water has been removed, the reaction mixture is subjected to fractional distillation. The portion boiling at 110- 111 C./ 100 mm. Hg is isolated. The yield of pure dipropargyl formal (B.P. 172.5 C./ 760 mm. 12 1.4440, Sp. Gr. -0.9 87) is 260 grams or about 70% of theoretical.

The dipropargyl formal per se is insoluble in water, but when present in an amount up to 5% by volume in propargyl alcohol, the mixture is soluble in water at a 1% concentration and also soluble at the same concentration in the foregoing acids .and aqueous solutions thereof. The inhibitor mixture is soluble in various concentractions of non-oxidizing acids, even commercial hydroch=loric acid of about 37% strength. Aqueous solutions of such acids usually contain from 1 to 15 by weight of acid to which the inhibitor mixture is added in the ice aforestated amounts to yield the corrosion preventive composition.

The corrosion preventive composition of the present invention will inhibit the corrosion of various metals such as iron, steel, nickel and ferrous alloys when in contact with said composition. The-corrosion preventive composition is ideal for use in metal-pickling, metal cleaning and polishing baths, boiler cleaning and as corrosion inhibitor of oil-well casing and tubing.

The inhibitor mixture of the present invention is effective at a temperature ranging from room to 212 F. The limit of the latter temperature is dependent on the concentration of the acid used in practical application or in the test, the more dilute the acid, i.e., at about 5% concentration, the higher the temperature limit of the inhibitor mixture. i

In order to demonstrate the eifectiveness of our inhibitor mixture, a series of tests was Fill). in which 0.4% by volume of the inhibitor mixture was put into a 15 by weight of aqueous solution'of hydrochloric acid held at 200 F. and a N- steel coupon, previously pickled, cleaned, dried and weighed was suspended in the acid for 16 hours. As controls, 0.4% by volume of each of propargyl alcohol and a dipropargyl formal were placed separately in the same acid and the procedure repeated. The coupons were then washed, dried and reweighed to determine the appearance and the amount of metal dissolved by the acid. This was calculated as milligrams of weight loss. Results of these tests are shown in I 108.8 Slight pitting. Dipropargyl formal 82.2 Clean. Inhibitor mixture by olume of propargyl alcohol and 5% by volume of dipropargyl formal) 70 Clean.

From the foregoing results, it is clearly evident that inhibitor mixture is far superior to propargyl alcohol. In view of this finding, we prepared the acetal and the acetaldehyde of propargyl alcohol and found that results paralleling those for dipropargyl formal shown in Table 1 were obtained under the same test. Improved results were obtained when the dipropargyl formal was dispersed in the aqueous acid by means of an ionic or non-ionic surface active agent that is stable in aqueous non-oxidizin g acid. The ratio of formal should be 3 parts to 1 part of surfactant, our preference being non-ionic surfactants obtained by the condensation of 1 mole of diisobutyl phenol with 6 to 10 moles of ethylene oxide.

Improved results are also obtained when the inhibitor mixture is blended with a quaternized N-heterocyclic base and the preferred surfactant in the ratio of 5:4:1 parts by weight, respectively. Representative of such bases are those disclosed in US. Patents 2,037,762; 2,080,553; 2,403,153; 2,606,873; and 2,814,593. In lieu of such bases, various amines or mixtures thereof, such as primary, secondary or tertiary aliphatic amines, i.e., butylamine, dibutylamine, tributylamine, amylamine, diamylamine, triamylamine, etc., heterocyolic amines, i.e., alkylpyridines, preferably those known as alkylpyridines =HB, a commercially available mixture of alkylated pyridines having an average molecular Weight of 170, may be used to yield improved results.

We claim:

1. An aqueous solution consisting essentially of an aqueous solution of a non-oxidizing acid, having an acid concentration of from 1 to 15% by weight and from 0.001 to 1.0% by volume based on the volume of said aqueous acid of a corrosion inhibiting mixture consisting of 95% by volume of propargyl alcohol and 5% by volume of dipropargyl formal.

2. A corrosion inhibited mineral acid consisting essentially of an aqueous solution of mineral acid in a concentration of from 1 to 15% by Weight and containing from 0.001 to 1.0% by volume based on the volume of said aqueous acid of a corrosion inhibiting mixture consisting of 95% by volume of propargyl alcohol and 5% by volume of dipropargyl formal.

3. A corrosion inhibited aqueous hydrochloric acid solution consisting of from 1 to 15 by weight of hydrochloric acid inhibited against corrosion by the addition thereto of from 0.001 to 1.0% by volume of a composition consisting of 95% by volume of propargyl alcohol and 5% by volume of dipropargyl formal.

4. A process [for inhibiting the corrosion of a metal of the group consisting of iron, steel, nickel and ferrous alloys by aqueous mineral acid in a concentration of from 1 to 15 .by Weight in contact therewith, which consists of maintaining in said acid from 0.001 to 1.0% by volume based on the volume of said aqueous acid of a corrosion inhibiting mixture consisting of 95% by volume of propargyl alcohol and 5% by volume of dipropargyl formal.

References Cited by the Examiner UNITED STATES PATENTS 8/1951 Fahnoe 260-6 15 XR 4/1962 Oakes 252-146 XR 10/1963 Harrison et a1. 252-146 XR FOREIGN PATENTS 12/1963 Canada.

OTHER REFERENCES Acetylenic Corrosion Inhibitors, Industrial and Engineering Chemistry, vol. 51, No. 7, July 1959, pages SAMUEL H. BLECH, Primary Examiner.

ALBERT T. MEYERS, Examiner.

S. E. DARDEN, Assistant Examiner. 

1. AN AQUEOUS SOLUTION CONSISTING ESSENTIALLY OF AN AQUEOUS SOLUTION OF A NON-OXIDIZING ACID, HAVING AN ACID CONCENTRATION OF FROM 1 TO 15% BY WEIGHT AND FROM 0.001 TO 1.0% BY VOLUME BASED ON THE VOLUME OF SAID AQUEOUS ACID OF A CORROSION INHIBITING MIXTURE CONSISTING OF 95% BY VOLUME OF PROPRGYL ALCOHOL AND 5% BY VOLUME OF DIPROPARGYL FORMAL. 